FIDELITY OF OPTICAL-PHASE CONJUGATION BY PHOTOREFRACTIVE DEGENERATE 4-WAVE-MIXING IN BARIUM-TITANATE

The fidelity of optical phase conjugation resulting from photorefractive degenerate four-wave mixing in barium titanate was investigated using an interferometric technique. The effect on the fidelity of varying the relative intensities of the beams entering the crystal was studied. It was found that the intensity of the image to be conjugated as a fraction of the total intensity in the crystal is the dominant factor. The effects of angular misalignment of the incident laser beams were investigated and a strict angular criterion established. The angular tolerance appears to be determined by the Bragg diffraction criterion for infinite plane waves, which may be much less than the divergence of the image bearing beam to be phase conjugated.